The present invention relates to methods and tools used in failure analysis of integrated circuit (IC) products in the semiconductor industry, and more particularly to a method of mechanically grinding and polishing a packaged semiconductor die (also called an IC chip) in a manner that protects the die from electrical and physical damage, and an apparatus for carrying out the method.
IC circuits fail due to various electrical, physical, or chemical mechanisms such as electrical overstress, wear out, or contamination. Some failure analysis approaches and procedures require a die substrate to be precisely ground down to a particular thickness, then polished, in order to implement certain tests such as infrared or emission microscope analysis to locate such mechanisms. The most well known method of mechanically grinding and polishing a die involves progressively grinding the die or chip down to a desired thickness using a die holder, an abrasive, and a rotatable wheel, and then polishing the die substrate surface. For both grinding and polishing, the die holder applies the die to the abrasive, which is attached to the rotatable wheel.
The die holders currently used are often problematic in their implementation. The conventional and most popular method of using such a holder consists of essentially three steps. First, the user by conventional means exposes a die to be ground and polished. Second, the user secures the device (die and die package) to the holder. Third, the user applies the die to an abrasive, which is supported by a rotatable wheel.
The disadvantage of the conventional method is that the device is likely to lose functionality, which would end the analysis of the device. This typically occurs for several reasons. First, because the user handles the holder by hand, electrostatic discharge from the user's fingers to the holder and device can damage the device. Second, physical damage from the user's fingers inadvertently bending the device leads can be problematic. Third, adhesive wax used to attach the device to the holder builds up between the device leads, removal of which is tedious and time consuming. The prior art has not adequately addressed these concerns and has therefore fallen short of producing desired and reliable results.
Known methods of preventing such electrical and physical damage or of eliminating the prior art wax problem are inadequate to present technological needs. A need therefore remains for a mechanical die grinding and polishing method and apparatus that preserves the functionality of the device when grinding and polishing a die.